Spinal stenosis can occur when the spinal canal narrows to compress the spinal cord or associated nerves roots. Spinal degeneration often occurs with aging, but may also be caused by disc herniation, osteoporosis, cancerous growth, or arise as a congenital condition. Spinal stenosis may also be caused by subluxation, facet joint hypertrophy, osteophyte formation, underdevelopment of spinal canal, spondylosis deformans, degenerative intervertebral discs, degenerative spondylolisthesis, degenerative arthritis, ossification of the vertebral accessory ligaments, or thickening of the ligamentum flavum. A less common cause of spinal stenosis, which usually affects patients with morbid obesity or patients on oral corticosteroids, is excess fat in the epidural space. The excessive epidural fat compresses the dural sac, nerve roots and blood vessels contained therein, often resulting in back and leg pain, or weakness and numbness of the legs.
Spinal stenosis may affect the cervical, thoracic, or lumbar regions of the spine. In some cases, spinal stenosis may be present in all three regions. Lumbar spinal stenosis can cause lower back pain, abnormal sensations in the legs or buttocks, and loss of bladder or bowel control.
Patients suffering from spinal stenosis are typically first treated with exercise therapy, analgesics, or anti-inflammatory medications. If these conservative treatment options fail, surgery may be required to decompress the spinal cord or nerve roots.
Traditional surgical procedures to correct stenosis in the lumbar region require a large incision be made in the patient's back. Muscles and other supporting structures are then stripped away from the spine, exposing the posterior aspect of the vertebral column. A portion of the vertebral arch, often at the laminae, may then be removed (laminectomy). The procedure is usually performed under general anesthesia. Patients can be admitted to the hospital for approximately five to seven days depending on the age and overall condition of the patient. Patients often require between six weeks and three months to recover from the procedure. Further, many patients need extended therapy at a rehabilitation facility to regain enough mobility to live independently.
Spinal stenosis can also occur due to compression of the intervertebral foramina, the passages between vertebrae through which nerves pass laterally from the spinal cord to the body. Foramina compression is often due to unwanted bone, ligament, or scar tissue formation in the passages. A foraminotomy can relieve the symptoms of nerve compression caused by foramen constriction. Traditional treatments include making an incision in the back of the patient's neck, then peeling away muscle to reveal the bone underneath, and cutting a small hole in the vertebra. Through this hole, using an arthroscope, the foramen can be visualized, and the impinging bone or disk material removed.
Much of the pain and disability after an open foraminotomy or laminectomy results from the tearing and cutting of the back muscles, blood vessels, supporting ligaments, and nerves. Also, because the spine stabilizing back muscles and ligaments are stripped and detached from the spine, these patients frequently develop spinal instability post-operatively.
Minimally invasive techniques offer the potential for less post-operative pain and faster recovery compared to traditional open surgery. Percutaneous spinal procedures can be performed with local anesthesia, thereby sparing the patient the risks and recovery time required with general anesthesia. In addition, there is less damage to the paraspinal muscles and ligaments with minimally invasive techniques, thereby reducing pain and reducing damage caused to the stabilizing structures.
Various techniques for minimally invasive treatment of the spine are known. Microdiscectomy is performed by making a small incision in the skin and deep tissues to create a portal to the spine. A microscope is then used to aid in the dissection of the adjacent structures prior to discectomy. The recovery for this procedure is much shorter than traditional open discectomies.
Percutaneous discectomy devices with fluoroscopic guidance have been used successfully to treat disorders of the disc but not to treat spinal stenosis directly. Arthroscopy or direct visualization of the spinal structures using a catheter or optical system have also been proposed to treat disorders of the spine including spinal stenosis, however these devices still use miniaturized standard surgical instruments and direct visualization of the spine similar to open surgical procedures. These devices and techniques are limited by the small size of the spinal canal and these operations are difficult to perform and master. In addition, these procedures are painful and often require general anesthesia. Further, arthroscopy procedures are time consuming and the fiber optic systems are expensive to purchase and maintain.
Current surgical procedures to treat spinal stenosis are often highly invasive, requiring significant removal of tissue to access the site and treat the stenotic lesion. A typical open procedure requires an incision be large enough to permit a surgeon to directly visualize the surgical site. Alternatively, an endoscope may be used in conjunction with a tissue retraction system to allow visualization and tissue removal through a large portal. Both procedures are highly invasive compared to the presently disclosed methods described herein. These traditional procedures often adversely affect the patient due to higher blood loss during the procedure, more damage to the tissue, or a larger incision. These factors may require longer hospital stay and longer rehabilitation time for the patient.
There are no known spinal procedures that employ percutaneous decompression of an exiting nerve root in the lateral recess area of the lumbar spine. Difficulties in performing a percutaneous procedure include lack of visualization of the surgical site, and wide variations in the anatomical region where bone is being removed. The variation (i.e. thickness and geometry) in the lateral aspect of the lamina where bone is being removed can make it difficult for surgical instruments to grasp, cut, and remove bone percutaneously. Hence, it remains desirable to provide simple methods, techniques, and devices for treating spinal stenosis and other spinal disorders without the disadvantages of conventional techniques.